It's a known trend: Angry Young Men turn into mean old ones. One minute you're the blazing voice of youth, raging against the Establishment and proclaiming freedom all round; flash forward a few decades, and the same voice is grumbling in its club about the maitre d' being Jewish and insisting on getting its keys back because it's quite sober enough to drive home, dammit. Consider Kingsley Amis, for instance, author of Lucky Jim, whose biography can, notably be found here on the Modern Drunkard Magazine>, which includes such remarks as 'Although talk was one of Amis’s great joys, he had little use for women’s conversation...' and his comment that Nelson Mandela should be hanged. Or consider John Osborne, saviour of theatre in the 1950s, whose plays got worse and worse while he passed away his leisure hours by such activities as casting out his teenage daughter for preferring to hang around with her friends than his, and taking advantage of his fourth wife's suicide, which lifted the restraining order laid down during their divorce, to add an entire new chapter to his autobiography slamming her. Politically, people like this tend to move from left to right as they age; personally, they tend to wear down or burn through those around them.

Why this trend? How do you go from being the voice of freedom to the voice of intolerance? The answer, I think, lies in the desire for power.

People are naturally adaptable; the tendency to always have been at war with Eurasia is a common failing. When we change our circumstances, it can take an effort of will not to change our sympathies. Some people are more inclined to consistency than others, but a wilful temperament is seldom a self-examining one. In certain cases, the trajectory is almost predictable.

What the angry young man and the mean old man have in common is aggression, aggression and a desire to have their own way. Young men, on the whole, do not have very much: they have yet to make their fortunes, the majority of power is held by their elders, they have no children to challenge them from below. In that circumstance, knocking down the Establishment makes self-interested sense: you're not in it, and if it topples, your chance of clambering up the rubble looks fair. Political anger can be principled, or it can simply be a politicised expression of frustration at not having what others have, and wanting it.

But bring the same person forward thirty years, and he's got quite a lot. He has money; he's in the generation that now holds power; the kind of challenges that he used to issue to his elders are now coming from his juniors -... and they want what he has. If he has a sharing disposition, this may not threaten him so much, but his original rage against the Establishment was not really motivated by a desire to see things meted out fairly, but by a desire to get as much as he could as quickly as possible. A fair-minded young man becomes a fair-minded old one, unless something dreadful happens to him along the way, and can move gracefully from demanding cooperation to trying to give the young ones a hand up - but a greedy young man is not about to share anything with younger men making the demands he used to make. Why should he? That would mean he had less.

So what you end up with is an apparent turncoat, a man who's moved from being a rebel to being a defender of the fortress, with no sense of personal inconsistency. He didn't really want the fortress open, he just wanted what was in it, and now he's inside, he wants the door barred. But he hasn't actually changed sides; he was never on anyone's side but his own to begin with.

There's also the question of venting. Molly Ivins famously remarked, 'Satire is traditionally the weapon of the powerless against the powerful. I only aim at the powerful. When satire is aimed at the powerless, it is not only cruel - it's vulgar.' Someone who has a disposition for invective, a streak of sadism, needs somewhere to put it. When he's powerless, the powerful are a great target: lots of people come on your side when you take aim on the powerful, and you have nothing much to lose anyway. But once he becomes powerful, that's no longer a safe target. Say too many vicious things about your fellow grandees, and they might kick you out of the club. Moving to attack the powerless becomes, once again, the safest option. There's not much they can do about it, and anyway, it's fun to kick someone who can't kick back; it allows you to enjoy your own fortunate status. Of course, it is cruel and vulgar, but who cares? The only bad effect that can have on you is if people complain about it, and for a combative person, that's just more opportunities to blast invective.

I don't say any of this to imply that anyone who seems politically left-wing or who rages against the machine as a youngster will turn into a sour old fogey. Some people are born rebels and stay rebels; generally, they find new causes, broaden their interests, and keep talking about what interests them. As Bob Geldof remarked of his support for Father's Rights, 'It's not in my nature to shut up.' Some people get stirred up about what they consider injustices; different people may take different views of where justice lies, but some people keep agitating for it, however they see it. Similarly, some people are born inclined to preserve the status quo, and go through lives accepting change only cautiously. Either of these are reasonable ways to go through life. But you want to listen out for the most vicious tongues; in the end, do they really love the position they're espousing, or to they just love having something to be vicious about?

In the end, it comes down to compassion for people. Is someone angry about a state of affairs because it hurts people, or because they need something to be angry about? Do they struggle to keep their anger directed towards ends that make things better, or do they use other people as target practice? In life as well as in fiction, anger can be gratuitous.